Any lawful gun owner may open carry on private property with permission of the property owner, with exception to prohibited places. The State is not prohibiting you from open carrying the private business are. Would Open Carry allow me to walk into any gun shop with a loaded firearm openly displayed? What about a courthouse or police station?
That's not in Florida law though as a protection it's just something INSIDE you aren't likely to see enforcement nor report upon.
750.25 2.n states
A person possessing weapons or firearms at his or her home or place of business;
This is what your gun store employee is riding on as place of business and they and pawn shops along with (I) where they have explicit inclusion which is partially redundant to n however a bit more broad to employees with the terms agent/representative.
You could have a furniture store owner make a similar choice and we rarely see that asserted since its not really a social norm.
Notice it's at "his or her home" which home or house generally falls as dwelling not 'land' and since your friends might be your employees your house is likely not their place of business so there is nothing I've found in 790 that covers that.
This is what makes the jon leggett case in Volusia interesting. He was outside on his property but not in his house/home.
Although 'primary domicile' is not referenced the term 'home' is as in 'any house you own' however in it is implied.
Besides what's covered by 725.25 open carry is restricted by the state as it is prohibited with listed exceptions for lawful use.
If you don't have a range at your property that's a legal range outside gets to be a grey area. I do believe 725.25 especially 2n requires a modification to specifically state property boundaries and allow for permission to others which it currently doesn't unless other exceptions are present such as a lawful safe range as one example.
790.06 already makes a courtroom illegal concealed or not.